1. Technical Field
The present invention relates to a virtual image display device such as a head-mounted display mounted on a head.
2. Related Art
Recently, as virtual image display devices that enable formation and observation of virtual images like head-mounted displays, various devices of a type of guiding image light from a display element to eyes of an observer using a light guide plate have been proposed (see Patent Document 1 (JP-A-2008-172367) and Patent Document 2 (JP-A-2000-249969)). For example, see-through systems that can superimpose image light and external light by incorporating hologram elements in the light guide plates have been proposed (see Patent Document 3 (JP-A-2007-240924)). Further, not for the head-mounted display, a technology of providing a hard coating layer for protection of surfaces of resin molded components has been generally known (see Patent Document 4 (JP-A-2009-51920)).
In the head-mounted display, in order to guide image light in an appropriate condition, it is necessary to keep the surface part of the light guide plate for propagation processing of the image light by reflection or the like in good condition. Therefore, it is conceivable that a hard coating layer is provided for prevention of damage on the surface part and easy removal of soiling on the surface. Particularly, in the case of the see-through head-mounted display, the exposed parts of the light guide plate are likely to increase and provision of the hard coating layer in the surface part becomes more important. Here, in deposition of the hard coating layer, cleansing is generally performed for elimination of fouling in the surface part immediately before deposition.
However, it is necessary to provide various optical elements for guiding light such as the hologram element in Patent Document 3, for example, in the light guide part of the head-mounted display. Accordingly, for example, if cleansing is performed as pre-processing of the deposition of the hard coating layer, the optical elements provided in the light guide part may be separated and otherwise, light guide performance or the like may be deteriorated.